4R75E downshift flare
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From: Sioux Falls Area
4R75E downshift flare
Hauled my in-law's pop-up camper across the great state of South Dakota this week and noticed that when downshifting from 4th to 3rd it would occasionally flare a bit on the downshift. it was a real quick 100-200 rpm flare when it did it.
it would not always flare, though, so it took me a while to figure out a deciding factor. (I had time, as it was about an 8hr haul with kids).
what I finally noticed is that if the trans temp was below 180°F, the downshift was solid - no discernible flare. but if the temp got north of 180°F, then it would flare a bit and never seem to "learn" it's way out of the flare until the temp dropped below 180°
the ambient temp was between 95°-104° on the trip, and the trans seemed to run between about 170°-190° depending on how hilly the terrain was.
it didn't downshift a lot. I could pull most of the hills in OD, even if it had to unlock the converter.
is this a sign of anything?
thanks
it would not always flare, though, so it took me a while to figure out a deciding factor. (I had time, as it was about an 8hr haul with kids).
what I finally noticed is that if the trans temp was below 180°F, the downshift was solid - no discernible flare. but if the temp got north of 180°F, then it would flare a bit and never seem to "learn" it's way out of the flare until the temp dropped below 180°
the ambient temp was between 95°-104° on the trip, and the trans seemed to run between about 170°-190° depending on how hilly the terrain was.
it didn't downshift a lot. I could pull most of the hills in OD, even if it had to unlock the converter.
is this a sign of anything?
thanks
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From: Sioux Falls Area
Thanks for responding, mark.
The fluid was last changed about 50k miles ago.
Currently 161k on the clock.
The change at 109k appeared to be the first and was done with an exchange machine via cooler lines. The fluid used was a synthetic (presumed to be BG brand).
I didn't realize the 4r70 series were notably hard on fluid, other than the known TCC shudder that plagued them in the pre Mercon V days.
The fluid was last changed about 50k miles ago.
Currently 161k on the clock.
The change at 109k appeared to be the first and was done with an exchange machine via cooler lines. The fluid used was a synthetic (presumed to be BG brand).
I didn't realize the 4r70 series were notably hard on fluid, other than the known TCC shudder that plagued them in the pre Mercon V days.
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From: Sioux Falls Area
So my curiosity is killing me ....
What is it about the 4r70's that make them hard on fluid?
They seem so much more simple in nature than, say, the 6r80.
Just really curious.
What is it about the 4r70's that make them hard on fluid?
They seem so much more simple in nature than, say, the 6r80.
Just really curious.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,714
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From: SE Florida
Mostly I've found that it is the programming that controls the converter clutch. This trans seems to have longer lockup times on the converter and allows some controlled slip on the converter clutch.
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